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Silhouette by Kevin Gosse

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Name: Silhouette

A library to build .NET profilers in .NET. No need for C++ anymore, just C#.

Author: Kevin Gosse

NuGet: https://www.nuget.org/packages/Silhouette/

You can find more details at https://github.com/kevingosse/Silhouette

Source: https://github.com/kevingosse/Silhouette

Author​

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Kevin Gosse Alt text

Original Readme​

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Silhouette - A library to build .NET profilers in .NET

Quick start

Create a new C# NativeAOT project. Reference the Silhouette nuget package and add a class inheriting from Silhouette.CorProfilerCallback11Base (you can use a different version of CorProfilerCallbackBase depending on the version of .NET you're targeting). Override the Initialize method. It will be called with the highest version number of ICorProfilerInfo supported by the target runtime.


using Silhouette;

[Profiler("0A96F866-D763-4099-8E4E-ED1801BE9FBC")] // Use your own profiler GUID here
internal partial class CorProfilerCallback : CorProfilerCallback11Base
{
    protected override HResult Initialize(int iCorProfilerInfoVersion)
    {
        if (iCorProfilerInfoVersion < 11)
        {
            return HResult.E_FAIL;
        }

        var result = ICorProfilerInfo11.SetEventMask(COR_PRF_MONITOR.COR_PRF_ENABLE_STACK_SNAPSHOT | COR_PRF_MONITOR.COR_PRF_MONITOR_THREADS);

        return result;
    }
}

The Profiler attribute triggers a source-generator that emits the proper DllGetClassObject function and validates that the user is using the matching guid for the profiler. Alternatively, you can manually implement a DllGetClassObject method that will be called by the .NET runtime when initializing the profiler. Use the built-in ClassFactory implementation and give it an instance of your CorProfiler class.

using Silhouette;
using System.Runtime.InteropServices;

internal class DllMain
{
     // This code is automatically generated when using the `[Profiler]` attribute on `CorProfilerCallback`
    [UnmanagedCallersOnly(EntryPoint = "DllGetClassObject")]
    public static unsafe HResult DllGetClassObject(Guid* rclsid, Guid* riid, nint* ppv)
    {
        // Use your own profiler GUID here
        if (*rclsid != new Guid("0A96F866-D763-4099-8E4E-ED1801BE9FBC"))
        {
            return HResult.CORPROF_E_PROFILER_CANCEL_ACTIVATION;
        }

        *ppv = ClassFactory.For(new CorProfilerBase());

        return HResult.S_OK;
    }
}

CorProfilerXxBase offers base virtual methods for all ICorProfilerCallback methods, so override the ones you're interested in:

    protected override HResult ThreadCreated(ThreadId threadId)
    {
        Console.WriteLine($"Thread created: {threadId.Value}");
        return HResult.S_OK;
    }

Use the ICorProfilerInfoXx fields to access the ICorProfilerInfo APIs:

    private unsafe string ResolveMethodName(nint ip)
    {
        try
        {
            var functionId = ICorProfilerInfo11.GetFunctionFromIP(ip).ThrowIfFailed();
            var functionInfo = ICorProfilerInfo2.GetFunctionInfo(functionId).ThrowIfFailed();
            using var metaDataImport = ICorProfilerInfo2.GetModuleMetaDataImport(functionInfo.ModuleId, CorOpenFlags.ofRead).ThrowIfFailed().Wrap();
            var methodProperties = metaDataImport.Value.GetMethodProps(new MdMethodDef(functionInfo.Token)).ThrowIfFailed();
            var typeDefProps = metaDataImport.Value.GetTypeDefProps(methodProperties.Class).ThrowIfFailed();

            return $"{typeDefProps.TypeName}.{methodProperties.Name}";
        }
        catch (Win32Exception)
        {
            return "<unknown>";
        }
    }

Most methods return an instance of HResult<T>. You can deconstruct it into a (HResult error, T result) and manually check the error code. You can also use the ThrowIfFailed() method that will return only the result and throw a Win32Exception if the error code is not S_OK.

About​

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Profiling .net applications

Measuring performance improvements

How to use​

Example (source csproj, source files)​

This is the CSharp Project that references Silhouette

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>net10.0</TargetFramework>
    <ImplicitUsings>enable</ImplicitUsings>
    <Nullable>enable</Nullable>
	  <PublishAot>true</PublishAot>
	  <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
  </PropertyGroup>

  <ItemGroup>
    <PackageReference Include="Silhouette" Version="3.2.0" />
  </ItemGroup>
	
	<PropertyGroup>
		<EmitCompilerGeneratedFiles>true</EmitCompilerGeneratedFiles>
		<CompilerGeneratedFilesOutputPath>$(BaseIntermediateOutputPath)\GX</CompilerGeneratedFilesOutputPath>
	</PropertyGroup>
	
</Project>

Generated Files​

Those are taken from $(BaseIntermediateOutputPath)\GX

namespace Silhouette._Generated
{
    using System;
    using System.Runtime.InteropServices;

    file static class DllMain
    {
        [UnmanagedCallersOnly(EntryPoint = "DllGetClassObject")]
        public static unsafe HResult DllGetClassObject(Guid* rclsid, Guid* riid, nint* ppv)
        {
            if (*rclsid != new Guid("8ad62131-bf21-47c1-a4d4-3aef5d7c75c6"))
            {
                return HResult.CORPROF_E_PROFILER_CANCEL_ACTIVATION;
            }

            *ppv = ClassFactory.For(new global::ProfilerDemo.MyProfiler());
            return HResult.S_OK;
        }
    }
}

Useful​

Download Example (.NET C#)​

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Download Example project Silhouette

Share Silhouette​

https://ignatandrei.github.io/RSCG_Examples/v2/docs/Silhouette

Category "Profiler" has the following generators:​

1 Silhouette Nuget GitHub Repo stars 2025-12-16

See category​

Profiler